OBSERVATION OF STEP FORMATION ON VICINAL SI(111) SURFACES BY ATOMIC FORCE MICROSCOPY

We have used atomic force microscopy (AFM) to study step structures on Si(111) surfaces induced by annealing at temperatures between 1503 and 1603 K with DC current for 20-160 s. The direction of step-bunches on the surfaces, which was determined by the misorientation direction of th, substrate, was the same for samples annealed at different temperatures. The monatomic steps on a terrace, however. were oriented parallel to the crystallographic low-index directions on samples annealed at 1553 K, whereas they were well aligned along the misorientation direction on samples annealed at 1593 K. The transition of the monatomic step direction seems to have occurred at around 1580 K. The misorientation angle measured by AFM was macroscopically in agreement with X-rav diffraction measurements.